On Tue, Oct 10, 2017 at 1:31 PM, David Rowley <david.row...@2ndquadrant.com> wrote: > > I don't think there's any need to invent any new GUC. You could just > divide cpu_tuple_cost by something. > > I did a quick benchmark on my laptop to see how much Append really > costs, and with the standard costs the actual cost seems to be about > cpu_tuple_cost / 2.4. So probably cpu_tuple_cost / 2 might be > realistic. create_set_projection_path() does something similar and > brincostestimate() does some similar magic and applies 0.1 * > cpu_operator_cost to the total cost. > > > # -- How does that compare to the cpu_tuple_cost? > # select current_Setting('cpu_tuple_cost')::float8 / 0.00416630302337493743; > ?column? > ---------------- > 2.400209476818 > (1 row) > > Maybe it's worth trying with different row counts to see if the > additional cost is consistent, but it's probably not worth being too > critical here. >
This looks good to me. I think it should be a separate, yet very small patch. -- Best Wishes, Ashutosh Bapat EnterpriseDB Corporation The Postgres Database Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers